# neighbor

### Syntax

neighbor bin_size neighbor_freq

• bin_size = non-negative real number

• neighbor_freq = positive integer

### Examples

neighbor 1. 100
neighbor 2. 200


### Description

This command sets parameters for updating the neighbor list. In CAC simulatoins, each atom in the atomistic domain and each integration point in the coarse-grained domain maintain neighbor lists. Note that the non-integration point interpolated atoms in the coarse-grained domain do not maintain neighbor lists because their force/energy etc. are not calculated.

bin_size, in Angstrom, sets the length of the bin, which adds to the cutoff distance $r_\mathrm{c}$ of the interatomic potential. All atoms within $r_\mathrm{c}$ + bin_size from an atom/integration point are the neighbors of this atom. Note that each edge length of the processor domain cannot be smaller than $2 \cdot$ ($r_\mathrm{c}$ + bin_size).

neighbor_freq is the frequency with which a check of whether the neighbor list should be updated is conducted. The neighbor lists of all atoms/integration points are updated if, with respect to the nodal/atomic positions recorded at the last check, any node or atom has a displacement larger than half the bin_size.

The initial number of neighboring atoms per atom/integration point is set in the limit command.

neighbor_init.f90 and update_neighbor.f90

### Default

neighbor 1. 200